1. Field of the Invention
The present invention relates to an integrated optical device and a fabrication method thereof.
2. Related Background Art
Integrated optical devices that have a semiconductor laser and an optical modulator that is optically coupled to the semiconductor laser provided on a substrate are known (See Japanese Application Laid Open No. H7-263655). Structures for implementing this optical coupling include Butt joint structures. This type of structure is formed as follows. First, an n-type cladding layer, an active layer and p-type cladding layer are formed on a substrate. Thereafter, an etching mask is formed on a p-type cladding layer in a region for forming a semiconductor laser. The n-type cladding layer, active layer and p-type cladding layer in a region for forming an optical modulator are then removed by means of dry etching by using the etching mask. Thereafter, an n-type cladding layer, absorption layer, and p-type cladding layer are grown in a region for forming an optical modulator.
However, the above method makes it difficult to control the etching depth when dry-etching the n-type cladding layer, active layer, and p-type cladding layer. As a result, the fluctuations in the etching depth between lots when fabricating the integrated optical device increase. Hence, the thickness of the n-type cladding layer formed in the region for forming the optical modulator must be adjusted again. In addition, when the fluctuations in the etching depth are large, it is difficult to match the height position of the absorption layer of the optical modulator with the height position of the active layer of the semiconductor laser. As a result, the optical coupling efficiency of the semiconductor laser and optical modulator is reduced.
Therefore, an object of the present invention is to provide a method of fabricating an integrated optical device that allows the etching depth to be controlled and an integrated optical device with a high coupling efficiency.